The cost to run a gas fireplace varies depending on the size of the unit, the gas utility company and the region in which you live, but you can figure out the cost of running your gas fireplace with a few simple calculations. You will need to know some rating information about your fireplace and the rates that you are paying for gas in your area.

### Gas Fireplace Ratings

Your gas fireplace is rated by the amount of British Thermal Units, or BTUs, that it consumes per hour. To determine how much your gas fireplace costs to run, you need to find the BTU rating of your unit. Look for a metal plate on the bottom or side of the unit that shows the BTU rating in the thousands.

### Gas Costs

Your region pays a certain amount for gas that can vary from time to time. If you look at your last gas bill, you should see the cost per "therm," which is the equivalent of 100,000 BTUs. If the information is not located on your bill, contact your gas provider to get the information.

### Computing the Therms per Hour

Divide the BTUs of your gas fireplace by 100,000 to get the therms per hour that the machine uses. For example, a gas fireplace with 25,000 BTUs of output would use .25 therms per hour.

### Computing the Cost

Multiply the therms used per hour by the cost per therm in your area to get the cost per hour of running your gas fireplace. In our example, if a therm costs 60 cents, .25 times 60 cents equals 15 cents. This means that every hour the fireplace is on, it costs 15 cents in gas. In this example, running the gas fireplace for 10 hours would cost 90p.